I've owned both, one Adamas and two Contegos (M4/coated and M390). I still own the Adamas.
If it weren't for the humidity here in the PNW, I'd have kept the M4 Contego a bit longer; I suspect the sharp edges on the handle would eventually have driven me to sell it.
The M390 Contego was gorgeous, with no sharp handle bits and a top-flight steel for corrosion resistance. But the handle is so long that, even with large hands (size L glove), I couldn't brace the butt in my palm to close the knife -- ironically, the sharp end of the base model M4 Contego made this effortless. The butt on the exclusive is so smooth that it just slipped out of my grip every time.
My Adamas has served me well as a knife, a hammer, and a screwdriver, and taken everything I've thrown at it without flinching. The D2 is fantastic, as are the beefed-up pivot and Axis bar. The massively thick handle does what it says on the tin.
I can't comment on sharpening angles, but I didn't buy the Adamas to be a slicer. For a thick knife, I've never had any issues cutting what I needed to cut with it.